Since 1970 Zeki has been based at University College, being appointed the Professor of Neurobiology in 1981 and most recently, Professor of Neuroesthetics . Here he details his theories on the intimate connections between the brain, the mind and experience

This has led us to enquire further into the extent to which
mathematics itself constitutes a study of the brain’s logical architecture; in
other words, the extent to which the study of mathematics also belongs in a branch
of biology and more specifically neurobiology.

We start by enquiring into the processes which led one of the
most interesting mathematicians of the last century, namely Srinivasa Ramanujan, to his conclusions.

They are
commonly referred to as INTUITION.

But what is intuition?

The term is commonly used to signify that a significant insight
or conclusion has been reached without thinking and without reasoning. This is
true in all languages to which we (the writers of this post) have access. One would
no doubt find definitions which are more sophisticated but, as the quotations
below show, the absence of logical process in having an intuition is the most
common definition and reflects, in fact, what the lay person usually means by
it.

The term has been much written about recently, especially since
the publication of a book about Ramanujan by Robert Kanigel entitled The Man who Knew Infinity, recently made
into a film.

Consider the following definitions of intuition, which exclude
any reasoning process:

Nor are such definitions restricted to Western European
languages. Much the same definition appears in Japanese.

"直感" = to capture things by feeling rather than
reasoning or discussion.

Or

"直観" is to directly understand the essence of
things without relying on reasoning.

We give these definitions in different languages only to show
that much the same applies to all. Central to most (but not all) definitions is
the absence of reasoning or logical thinking during the intuitive process or
its result. Hence, the dictionary definitions given do indeed reflect the way
in which the term is commonly understood.

Other definitions come closer to the arguments we give below;
they make no reference to the absence of reasoning logic, but only to the
absence of proof or evidence.

For example, the Merriam-Webster
and the Free Dictionary define
intuition as follows, respectively:

“A natural ability or power
that makes it possible to know something without any proof or evidence: a
feeling that guides a person to act a certain way without fully understanding
why”

“Something that is known or understood without
proof or evidence” (from
Merriam Webster)

“The faculty of knowing
or understanding something without reasoning or proof”

(from Free Dictionary )

which is not dis-similar to the definition given in the Great Soviet Encyclopaedia

(Intuition is an ability
to comprehend the truth through direct discovery without its justification with
the proof)

We propose below an alternative definition that may be obvious
to some but is not to many and therefore worth giving:

An intuition is an unconscious logical brain
process with an outcome or conclusion in the form of a statement or proposition. But whether the
outcome of the intuitive process is “right” or “wrong”, or “correct” or
“incorrect”, can only be determined by a
conscious logical process.

The closest dictionary definition to this that we know of is to
be found in the Russian Dictionary of
Psychology, which of course targets a more specialized audience:

(Intuition - thought process allowing almost instant finding of the
solutions to the problem with the lack of awareness of logical connections.)

Mathematics is a subject in which intuition is often invoked.

But
the end result of the unconscious logical process that is intuition can only be
“right” or “wrong” (correct or incorrect) when consciously scrutinized.

As examples of “right” and “wrong” mathematical intuitions
consider the following:

A right (correct) intuition: Pick a point at random on the
Earth (assume that the Earth is a sphere). The probability that the point
picked lies in the northern hemisphere is 50%.

Most students of mathematics (i.e. those who have enough
knowledge to understand the above statements, but who do not know if they are
right or wrong) would intuitively guess this statement to be true and it is.

A wrong (incorrect) intuition: Pick a real number randomly. The
probability that the real number picked is rational is zero.

Most mathematics students would intuitively guess this
statement to be false (you can obviously pick a rational number!). However, it
is correct.

But the conclusion that they are correct or incorrect can only be
reached through a conscious logical process.

Ramanujan was reluctant to submit his intuitions to the
conscious process of deductive logic, until Hardy brought him to England and
forced him to do so – i.e., to provide proofs for his intuitions – a conscious
process.

The absence of any logical process or reasoning in the
intuitive process is not the only weakness of the definitions of intuition;
some also exclude the role of experience in reaching conclusions through
intuition, as in the Larousse Dictionary
or the Dictionary.com definitions
given above.

We believe, however, that to have an
intuition in any area, one must have experience of that area or knowledge of it,
to provide a conclusion or statement, whether correct or incorrect.

Since we suspect that there is only a limited set of deductive logical
processes in the brain, it follows that the same logical processes must be used
to derive intuitions in different domains; what distinguishes intuitions in
different domains, and the logical processes that lead to them, is past
experience and knowledge in the relevant domain.

The result of this unconscious logical process (the intuition)
depends on initial conditions or inputs, which are based on previous (conscious) knowledge, consciously or unconsciously
obtained.

Our proposed definition raises interesting and important issues
and leads to the suggestion that

a.There are many (but a limited number of) logical
processes, which operate in the unconscious state.

b.These processes are undisciplined and unruly but still
obey some sort of brain logical process.

c.They become disciplined and eliminated by revisiting them,
and the conclusions to which they lead, in the conscious state.

d.The latter eliminates many of the undisciplined and
vagrant unconscious logical processing possibilities, thus stabilizing the
logical processing systems of the brain.

The study of intuition in mathematics thus belongs as well to
neurobiology. Or, put another way, mathematicians are also covert
neurobiologists.

Below are interesting comments received from Professor Mohanan, at IISER, Pune. Professor Mohanan is a linguist and educationalist.

As an educator, I have been interested in intuition for quite some time.

One of the difficulties that I experience when reading the literature on intuition is that it is used both as

a) a broad term for unconscious knowledge (tacit knowledge) and all unconscious cognitive operations, andb) specific unconscious operations such as perception and judgment That the outcome of intuition has not been achieved through rational or analytical means is clear, but exactly which unconscious process we are talking about seems to vary from author to author.

Take, for instance, Polany's idea of tacit knowledge and Chomsky's idea of grammar as the unconscious knowledge of the speaker of a language, and David Marr's idea of the vision as a cognitive module. We might say that grammar and vision are both subsumed under tacit knowledge. But if we say that, then it is meaningless to look for a single set of neural correlates for both, because they are not processed in the same place in the brain. Even for grammar, there is evidence to show that different intuitive judgments on the acceptability of linguistic forms are processed in different modules of mind-brain. (e.g. regular past tense as in raise-raised and irregular past tense as in buy-bought.)

Next, consider the distinction between slow and fast thinking that Kahnemann makes. When you use the word 'intuition', do you mean the same thing as fast thinking?

Take the distinction between perception and decision making. Does the term intuition cover both perception and unconscious decision making? Does it cover estimation (I can estimate, without counting, that the number of people in an auditorium is somewhere between 200 and 400). Does subitization come under intuition?

Does the term intuition cover what Poincarre called 'illumination' and what Csikszemtmihalyi called 'flow' (https://en.wikipedia.org/wiki/Mihaly_Csikszentmihalyi) Is this the same as the process involved in what people have called the 'aha' moment?

What is the distinction between naive intuition (which can be the same as uninformed prejudice) and the trained intuition of a mathematician?

There are autistic people who can 'perceive' prime numbers (e.g. http://www.danieltammet.net/blue-day.php) Is this the same as intuition?